Melatonin attenuates acute renal failure and oxidative stress induced by mercuric chloride in rats

Mirabegron, dependent on β3-adrenergic receptor, alleviates mercuric chloride-induced kidney injury by reversing the impact on the inflammatory network, M1/M2 macrophages, and claudin-2

The β3-adrenergic receptor (β3-AR) agonism mirabegron is used to treat overactive urinary bladder syndrome; however, its role against acute kidney injury (AKI) is not unveiled, hence, we aim to repurpose mirabegron in the treatment of mercuric chloride (HgCl2)-induced AKI. Rats were allocated into normal, normal + mirabegron, HgCl2 untreated, HgCl2 + mirabegron, and HgCl2 + the β3-AR blocker SR59230A + mirabegron. The latter increased the mRNA of β3-AR and miR-127 besides downregulating NF-κB p65 protein expression and the contents of its downstream targets iNOS, IL-4, -13, and -17 but increased that of IL-10 to attest its anti-inflammatory capacity. Besides, mirabegron downregulated the protein expression of STAT-6, PI3K, and ERK1/2, the downstream targets of the above cytokines. Additionally, it enhanced the transcription factor PPAR-α but turned off the harmful hub HNF-4α/HNF-1α and the lipid peroxide marker MDA. Mirabegron also downregulated the CD-163 protein expression, which besides the inhibited correlated cytokines of M1 (NF-κB p65, iNOS, IL-17) and M2 (IL-4, IL-13, CD163, STAT6, ERK1/2), inactivated the macrophage phenotypes. The crosstalk between these parameters was echoed in the maintenance of claudin-2, kidney function-related early (cystatin-C, KIM-1, NGAL), and late (creatinine, BUN) injury markers, besides recovering the microscopic structures. Nonetheless, the pre-administration of SR59230A has nullified the beneficial effects of mirabegron on the aforementioned parameters. Here we verified that mirabegron can berepurposedto treat HgCl2-induced AKI by activating the β3-AR. Mirabegron signified its effect by inhibiting inflammation, oxidative stress, and the activated M1/M2 macrophages, events that preserved the proximal tubular tight junction claudin-2 via the intersection of several trajectories.

Adverse effect propensity: A new feature of Gulf War illness predicted by environmental exposures

A third of 1990-1 Gulf-deployed personnel developed drug/chemical-induced multisymptom illness, "Gulf War illness" (GWI). Veterans with GWI (VGWI) report increased drug/exposure adverse effects (AEs). Using previously collected data from a case-control study, we evaluated whether the fraction of exposures that engendered AEs ("AE Propensity") is increased in VGWI (it was); whether AE Propensity is related to self-rated "chemical sensitivity" (it did); and whether specific exposures "predicted" AE Propensity (they did). Pesticides and radiation exposure were significant predictors, with copper significantly "protective"-in the total sample (adjusted for GWI-status) and separately in VGWI and controls, on multivariable regression. Mitochondrial impairment and oxidative stress (OS) underlie AEs from many exposures irrespective of nominal specific mechanism. We hypothesize that mitochondrial toxicity and interrelated OS from pesticides and radiation position people on the steep part of the curve of mitochondrial impairment and OS versus symptom/biological disruption, amplifying impact of new exposures. Copper, meanwhile, is involved in critical OS detoxification processes.

Anandamide modulates WNT-5A/BCL-2, IP3/NFATc1, and HMGB1/NF-κB trajectories to protect against mercuric chloride-induced acute kidney injury

Endocannabinoid anandamide (AEA) has a physiological role in regulating renal blood flow, whereas its analogs ameliorated renal ischemia/reperfusion injury. Nonetheless, the role of AEA against mercuric chloride (HgCl₂)-induced renal toxicity has not been unraveled. Rats were allocated into control, HgCl₂, and HgCl₂/AEA treated groups. The administration of AEA quelled the HgCl₂-mediated increase in inositol trisphosphate (IP3) and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). The endocannabinoid also signified its anti-inflammatory potential by turning off the inflammatory cascade evidenced by the suppression of high mobility group box protein-1 (HMGB1), receptor of glycated end products (RAGE), nuclear factor-κB p65 (NF-κB), and unexpectedly PPAR-γ. Additionally, the aptitude of AEA to inhibit malondialdehyde and boost glutathione points to its antioxidant capacity. Moreover, AEA by enhancing the depleted renal WNT-5A and reducing cystatin-C and KIM-1 (two kidney function parameters) partly verified its anti-apoptotic capacity, confirmed by inhibiting caspase-3 and increasing B-cell lymphoma-2 (BCL-2). The beneficial effect of AEA was mirrored by the improved architecture and kidney function evidenced by the reduction in cystatin-C, KIM-1, creatinine, BUN, and caspase1-induced activated IL-18. In conclusion, our results verify the reno-protective potential of AEA against HgCl₂-induced kidney injury by its anti-inflammatory, antioxidant, and anti-apoptotic capacities by modulating WNT-5A/BCL-2, IP3/NFATC1, HMGB-1/RAGE/NF-κB, caspase-1/IL-18, and caspase-3/BCL-2 cues.

Mechanisms of oxidative stress in methylmercury-induced neurodevelopmental toxicity

Methylmercury (MeHg) is a long-lasting organic environmental pollutant that poses a great threat to human health. Ingestion of seafood containing MeHg is the most important way by which it comes into contact with human body, where the central nervous system (CNS) is the primary target of MeHg toxicity. During periods of pre-plus postnatal, in particular, the brain of offspring is vulnerable to specific developmental insults that result in abnormal neurobehavioral development, even without symptoms in mothers. While many studies on neurotoxic effects of MeHg on the developing brain have been conducted, the mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity is less clear. Hitherto, no single process can explain the many effects observed in MeHg-induced neurodevelopmental toxicity. This review summarizes the possible mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity, highlighting modulation of Nrf2/Keap1/Notch1, PI3K/AKT, and PKC/MAPK molecular pathways as well as some preventive drugs, and thus contributes to the discovery of endogenous and exogenous molecules that can counteract MeHg-induced neurodevelopmental toxicity.

Melatonin ameliorates the drug induced nephrotoxicity: Molecular insights

BACKGROUND

Drug-induced nephrotoxicity is a frequent adverse event that can lead to acute or chronic kidney disease and increase the healthcare expenditure. It has high morbidity and mortality incidence in 40-70% of renal injuries and accounts for 66% cases of renal failure in elderly population.

OBJECTIVE

Amelioration of drug-induced nephrotoxicity has been long soughed to improve the effectiveness of therapeutic drugs. This study was conducted to review the melatonin potential to prevent the pathogenesis of nephrotoxicity induced by important nephrotoxic drugs.

METHODS

We analyzed the relevant studies indexed in Pubmed, Medline, Scielo and Web of science to explain the molecular improvements following melatonin co-administration with special attention to oxidative stress, inflammation and apoptosis as key players of drug-induced nephrotoxicity.

RESULTS

A robust consensus among researchers of these studies suggested that melatonin efficiently eradicate the chain reaction of free radical production and induced the endogenous antioxidant enzymes which attenuate the lipid peroxidation of cellular membranes and subcellular oxidative stress in drug-induced nephrotoxicity. This agreement was further supported by the melatonin role in disintegration of inflammatory process through inhibition of principle pro-inflammatory or apoptotic cytokines such as TNF-α and NF-κB. These studies highlighted that alleviation of drug-induced renal toxicity is a function of melatonin potential to down regulate the cellular inflammatory and oxidative injury process and to stimulate the cellular repair or defensive mechanisms.

CONCLUSION

The comprehensive nephroprotection and safer profile suggests the melatonin to be a useful adjunct to improve the safety of nephrotoxic drugs.

Mercury chloride toxicity in human erythrocytes: enhanced generation of ROS and RNS, hemoglobin oxidation, impaired antioxidant power, and inhibition of plasma membrane redox system

Mercury is among the most toxic heavy metals and a widespread environmental pollutant. Mercury chloride (HgCl₂) is an inorganic compound of mercury which is easily absorbed in the gastrointestinal tract and then enters the blood where it can interact with erythrocytes. In this study, the effect of HgCl₂ on human erythrocytes was studied under in vitro conditions. Erythrocytes were treated with different concentrations of HgCl₂ (1-100 μM) for 1 h at 37 °C. Cell lysates were prepared and assayed for several biochemical parameters. HgCl₂ treatment resulted in oxidation of ferrous iron of hemoglobin to ferric form giving methemoglobin which is inactive as an oxygen transporter. However, the activity of methemoglobin reductase was increased. Hemoglobin oxidation was accompanied by heme degradation and the release of free iron. Protein oxidation was greatly increased with a simultaneous decrease in free amino and sulfhydryl groups and glutathione content. The antioxidant power of HgCl₂-treated erythrocytes was impaired resulting in lowered metal reducing and free radical quenching ability of these cells. This suggests that HgCl₂ induces oxidative stress in human erythrocytes. This was confirmed when superoxide anion, hydrogen peroxide, peroxynitrite, and nitric oxide generation were found to be dose-dependently increased in HgCl₂-treated erythrocytes. Glycolysis and pentose phosphate pathway, the two major pathways of glucose metabolism in erythrocytes, were also inhibited. HgCl₂ treatment also inhibited the plasma membrane redox system while the activities of AMP deaminase and glyoxalase-I were increased. These results show that HgCl₂ induces oxidative and nitrosative stress, oxidizes hemoglobin, impairs the antioxidant defense mechanism, and alters metabolic pathways in human erythrocytes.

The multiple functions of melatonin in regenerative medicine

Melatonin research has been experiencing hyper growth in the last two decades; this relates to its numerous physiological functions including anti-inflammation, oncostasis, circadian and endocrine rhythm regulation, and its potent antioxidant activity. Recently, a large number of studies have focused on the role of melatonin in the regeneration of cells or tissues after their partial loss. In this review, we discuss the recent findings on the molecular involvement of melatonin in the regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others.

Does melatonin influence the apoptosis in rat uterus of animals exposed to continuous light?

Melatonin has been described as a protective agent against cell death and oxidative stress in different tissues, including in the reproductive system. However, the information on the action of this hormone in rat uterine apoptosis is low. Our objective was to evaluate the effects of melatonin on mechanisms of cell death in uterus of rats exposed to continuous light stress. Twenty adult Wistar rats were divided into two groups: GContr (vehicle control) and GExp which were treated with melatonin (0.4 mg/mL), both were exposed to continuous light for 90 days. The uterus was removed and processed for quantitative real time PCR (qRT-PCR), using PCR-array plates of the apoptosis pathway; for immunohistochemistry and TUNEL. The results of qRT-PCR of GEXP group showed up-regulation of 13 and 7, pro-apoptotic and anti-apoptotic genes, respectively, compared to GContr group. No difference in pro-apoptotic proteins (Bax, Fas and Faslg) expression was observed by immunohistochemistry, although the number of TUNEL-positive cells was lower in the group treated with melatonin compared to the group not treated with this hormone. Our data suggest that melatonin influences the mechanism and decreases the apoptosis in uterus of rats exposed to continuous light.

A novel approach to contrast-induced nephrotoxicity: the melatonergic agent agomelatine

OBJECTIVE

To study the potential nephroprotective role of agomelatine in rat renal tissue in cases of contrast-induced nephrotoxicity (CIN). The drug's action on the antioxidant system and proinflammatory cytokines, superoxide dismutase (SOD) activity, levels of glutathione (GSH) and malondialdehyde (MDA) and the gene expression of interleukin-6 (IL-6), tumour necrosis factor (TNF)-α and nuclear factor kappa B (NF-κB) was measured. Tubular necrosis and hyaline and haemorrhagic casts were also histopathologically evaluated.

METHODS

The institutional ethics and local animal care committees approved the study. Eight groups of six rats were put on the following drug regimens: Group 1: healthy controls, Group 2: GLY (glycerol), Group 3: CM (contrast media--iohexol 10 ml kg(-1)), Group 4: GLY+CM, Group 5: CM+AGO20 (agomelatine 20 mg kg(-1)), Group 6: GLY+CM+AGO20, Group 7: CM+AGO40 (agomelatine 40 mg kg(-1)) and Group 8: GLY+CM+AGO40. The groups were evaluated by one-way analysis of variance and Duncan's multiple comparison test.

RESULTS

Agomelatine administration significantly improved the serum levels of blood urea nitrogen (BUN) and creatinine, SOD activity, GSH and MDA. The use of agomelatine had substantial downregulatory consequences on TNF-α, NF-κB and IL-6 messenger RNA levels. Mild-to-severe hyaline and haemorrhagic casts and tubular necrosis were observed in all groups, except in the healthy group. The histopathological scores were better in the agomelatine treatment groups.

CONCLUSION

Agomelatine has nephroprotective effects against CIN in rats. This effect can be attributed to its properties of reducing oxidative stress and inhibiting the secretion of proinflammatory cytokines (NF-κB, TNF-α and IL-6).

ADVANCES IN KNOWLEDGE

CIN is one of the most important adverse effects of radiological procedures. Renal failure, diabetes, malignancy, old age and non-steroidal anti-inflammatory drug use pose the risk of CIN in patients. Several clinical studies have investigated ways to avoid CIN. Theophylline/aminophylline, statins, ascorbic acid and iloprost have been suggested for this purpose. Agomelatine is one of the melatonin ligands and is used for affective disorders and has antioxidant features. In this study, we hypothesized that agomelatine could have nephroprotective, antioxidant and anti-inflammatory effects against CIN in rats.

Effect of Selenium on the Levels of Cytokines and Trace Elements in Toxin-Mediated Oxidative Stress in Male Rats

Selenium is an essential cofactor in the key enzymes involved in cellular antioxidant defense. This study was designed to investigate the protective effects of selenium on mercury chloride (HgCl2)-induced toxicity. Male Wistar rats were randomly divided into four groups of six animals each. The first group was control; the second group was treated with mercuric chloride (HgCl2: 50 mg/kg/bw). The third group was treated with sodium selenite (Se 0.2 mg/kg/bw), and the fourth group received Se (0.2 mg/kg/bw) plus HgCl2 (50 mg/kg for 24 h). The influence of Se on mercury induced levels of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) and zinc, copper, and iron in serum of rats were observed. The serum MDA, SOD, zinc, and iron concentrations were found to be statistically different among the control and toxin-treated group. The serum levels of IL-6, IL-10, and TNF-α were also measured. There was a significant decrease in the levels of TNF-α, IL-6, and IL-10 in toxin-treated group II compared with that of the control group (p < 0.05). A significant increase in the serum levels of inflammatory cytokines IL-6, TNF-α, and IL-10 after administration of Se seemed to counteract some of the damage, as indicated by differences in the serum concentrations of major elements.

Metabolomics in nephrotoxicity

Nephrotoxicity or renal toxicity can be a result of hemodynamic changes, direct injury to cells and tissue, inflammatory tissue injury, and/or obstruction of renal excretion. Nephrotoxicity is frequently induced by a wide spectrum of therapeutic drugs and environ mental pollutants. Knowledge of the complex molecular and pathophysiologic mechanisms leading to nephrotoxicity remains limited, in part, by research that historically focused on single or relatively few risk markers. As such, current kidney injury biomarkers are inadequate in terms of sensitivity and specificity. In contrast, metabolomics enables screening of a vast array of metabolites simultaneously using NMR and MS to assess their role in nephrotoxicity development and progression. A more comprehensive understanding of these biochemical pathways would also provide valuable insight to disease mechanisms critical for drug development and treatment.

A review of metal-catalyzed molecular damage: protection by melatonin

Metal exposure is associated with several toxic effects; herein, we review the toxicity mechanisms of cadmium, mercury, arsenic, lead, aluminum, chromium, iron, copper, nickel, cobalt, vanadium, and molybdenum as these processes relate to free radical generation. Free radicals can be generated in cells due to a wide variety of exogenous and endogenous processes, causing modifications in DNA bases, enhancing lipid peroxidation, and altering calcium and sulfhydryl homeostasis. Melatonin, an ubiquitous and pleiotropic molecule, exerts efficient protection against oxidative stress and ameliorates oxidative/nitrosative damage by a variety of mechanisms. Also, melatonin has a chelating property which may contribute in reducing metal-induced toxicity as we postulate here. The aim of this review was to highlight the protective role of melatonin in counteracting metal-induced free radical generation. Understanding the physicochemical insights of melatonin related to the free radical scavenging activity and the stimulation of antioxidative enzymes is of critical importance for the development of novel therapeutic strategies against the toxic action of these metals.

Vitamin E improved cypermethrin-induced damages in the ovary of rats; evidence for angiogenesis and p53 involvement

This study aimed to investigate the protective effect of vitamin E (VitE) on cypermethrin (CPM)-induced damages in the ovary. Wistar rats were divided into seven groups (n=6) including; control-sham (c), CPM-received (CPM, 75 mg/kg, i.p.), and CPM and VitE-treated (VitE, 150 mg/kg, orally) for 7, 14 and 24 days. The antioxidant status determination and hormonal assays along with histological and immunofluorescent assessments were performed. The expression of p53 at mRNA level was also examined. The CPM administration affected the ovarian structure and functions as it elevated the follicular atresia and significantly (P<0.05) lowered the estradiol level, time dependently. VitE administration enhanced the CPM-reduced antioxidant capacity, gonadotropins and estradiol levels. Co-administration of VitE and CPM remarkably attenuated the CPM-induced RNA damage in granulosa and theca cells and elevated the deranged angiogenesis. The CPM-reduced micro and macro vessels distribution was significantly (P<0.05) elevated in the VitE-received animals. Expression of p53 at mRNA level was down regulated in the VitE-treated groups completely and relatively following 7 and 14 days, respectively. Our data showed that the CPM-induced biochemical and histological damages could be prevented by VitE. Moreover, protective effects of VitE attribute to its potency in enhancing the antioxidant capacity and promoting the gonadotropins secretion, which resulted in down regulation of p53 overexpression and RNA damage in follicular cells accomplished with improved angiogenesis.

Antioxidant effect of Arabic gum against mercuric chloride-induced nephrotoxicity

The effects of Arabic gum (AG) against nephrotoxicity of mercury (Hg), an oxidative-stress inducing substance, in rats were investigated. A single dose of mercuric chloride (5 mg/kg intraperitoneal injection) induced renal toxicity, manifested biochemically by a significant increase in serum creatinine, blood urea nitrogen, thiobarbituric acid reactive substances, and total nitrate/nitrite production in kidney tissues. In addition, reduced glutathione, glutathione peroxidase, and catalase enzymes in renal tissues were significantly decreased. Pretreatment of rats with AG (7.5 g/kg/day per oral administration), starting 5 days before mercuric chloride injection and continuing through the experimental period, resulted in a complete reversal of Hg-induced increase in creatinine, blood urea nitrogen, thiobarbituric acid reactive substances, and total nitrate/nitrite to control values. Histopathologic examination of kidney tissues confirmed the biochemical data; pretreatment of AG prevented Hg-induced degenerative changes of kidney tissues. These results indicate that AG is an efficient cytoprotective agent against Hg-induced nephrotoxicity by a mechanism related at least in part to its ability to decrease oxidative and nitrosative stress and preserve the activity of antioxidant enzymes in kidney tissues.

Tight junction proteins and oxidative stress in heavy metals-induced nephrotoxicity

Kidney is a target organ for heavy metals. They accumulate in several segments of the nephron and cause profound alterations in morphology and function. Acute intoxication frequently causes acute renal failure. The effects of chronic exposure have not been fully disclosed. In recent years increasing awareness of the consequences of their presence in the kidney has evolved. In this review we focus on the alterations induced by heavy metals on the intercellular junctions of the kidney. We describe that in addition to the proximal tubule, which has been recognized as the main site of accumulation and injury, other segments of the nephron, such as glomeruli, vessels, and distal nephron, show also deleterious effects. We also emphasize the participation of oxidative stress as a relevant component of the renal damage induced by heavy metals and the beneficial effect that some antioxidant drugs, such as vitamin A (all-trans-retinoic acid) and vitamin E (α-tocopherol), depict on the morphological and functional alterations induced by heavy metals.

Melatonin suppresses cisplatin-induced nephrotoxicity via activation of Nrf-2/HO-1 pathway

Background

Cisplatin, one of the most effective and potent anticancer drugs, is used in the treatment of a wide variety of both pediatric and adult malignancies. However, the chemotherapeutic use of cisplatin is limited by its serious side-effects such as nephrotoxicity and ototoxicity. Cisplatin chemotherapy induces a reduction in the antioxidant status, leading to a failure of the antioxidant defense against free-radical damage generated by antitumor drugs. Cisplatin-induced oxidative stress in the kidney was partially prevented by antioxidant treatments using superoxide dismutase, glutathione, selenium and flavonoids. Melatonin and its metabolites possess free-radical scavenging activity and it has been shown that they protect against cisplatin toxicity. However, the mechanism of the protective effects of melatonin against cisplatin-induced nephrotoxicity is still essentially unknown. We therefore designed this study to investigate the underlying mechanism of the protective effect of melatonin against cisplatin-induced renal damage in a rat nephrotoxicity model in vivo.

Methods

Twenty eight 8-week-old male Wistar rats were divided into four groups of control, melatonin treatment (4 mg/kg b.w i.p. for 10 days), cisplatin treatment (7 mg/kg b.w., i.p.) and melatonin and cisplatin combination treatment. Serum urea nitrogen (urea-N) and creatinine levels were measured. Histopathological changes were evaluated. In addition, we analyzed the expression levels of HO-1, Nrf2, NF-κB and AP-1 in Western blot analysis.

Results

Both serum creatinine and urea nitrogen increased significantly following cisplatin administration alone; these values decreased significantly with melatonin co-treatment of cisplatin-treated rats. Histological analysis showed that cisplatin caused damage in the proximal tubular cells in the kidneys of cisplatin-treated rats; these changes were reversed by melatonin co-treatment. Upon Western blot analysis, melatonin treatment increased Nrf2 accumulation in the nuclear fraction, and increased the expression of HO-1 in the cytosolic fraction as compared to the cisplatin-treated rats. Expressions of NF-κB p65 and AP-1 were increased significantly in the kidneys of rats treated with cisplatin compared with the expression in the kidneys from the control, melatonin-only-treated and melatonin co-treated rats.

Conclusion

Our present data suggest that melatonin attenuates cisplatin-induced nephrotoxicity possibly by modulating Nrf2/HO-1 signaling.

The role of metabolic biomarkers in drug toxicity studies

ABSTRACT Metabolic profiling is a technique that can potentially provide more sensitive and specific biomarkers of toxicity than the current clinical measures benefiting preclinical and clinical drug studies. Both nuclear magnetic resonance (NMR) and mass spectrometry (MS) platforms have been used for metabolic profiling studies of drug toxicity. Not only can both techniques provide novel biomarker(s) of toxicity but the combination of both techniques gives a broader range of metabolites evaluated. Changes in metabolic patterns can provide insight into mechanism(s) of toxicity and help to eliminate a potentially toxic new chemical entity earlier in the developmental process. Metabolic profiling offers numerous advantages in toxicological research and screening as sample collection and preparation are relatively simple. Further, sample throughput, reproducibility, and accuracy are high. The area of drug toxicity of therapeutic compounds has already been impacted by metabolic profiling studies and will continue to be impacted as new, more specific biomarker(s) are found. In order for a biomarker or pattern of biomarkers to be accepted, it must be shown that they originate from the target tissue of interest. Metabolic profiling studies are amenable to any biofluid or tissue sample making it possible to link the changes noted in urine for instance as originating from renal injury. Additionally, the ease of sample collection makes it possible to follow a single animal or subject over time in order to determine whether and when the toxicity resolves itself. This review focuses on the advantages of metabolic profiling for drug toxicity studies.

Gender related differences in kidney injury induced by mercury

The aim of this study was to determine if there are sex-related differences in the acute kidney injury induced by HgCl₂ since female rats express lower levels of renal Oat1 and Oat3 (transporters involved in renal uptake of mercury) as compared with males. Control males and females and Hg-treated male and female Wistar rats were employed. Animals were treated with HgCl₂ (4 mg/kg body weight (b.w.), intraperitoneal (i.p.)) 18 h before the experiments. HgCl₂ induced renal impairment both in male and female rats. However, female rats showed a lower renal impairment than male rats. The observed increase in kidney weight/body weight ratio seen in male and female rats following HgCl₂ treatment was less in the female rats. Urine volume and creatinine clearance decreased and Oat5 urinary excretion increased in both males and females, but to a lesser degree in the latter. Urinary alkaline phosphatase (AP) activity and histological parameters were modified in male but not in female rats after HgCl₂ administration. These results indicate that the lower Oat1 and Oat3 expression in the kidney of females restricts Hg uptake into renal cells protecting them from this metal toxicity. These gender differences in renal injury induced by mercury are striking and also indicate that Oat1 and Oat3 are among the main transporters responsible for HgCl₂-induced renal injury.

Melatonin membrane receptors in peripheral tissues: distribution and functions

Many of melatonin's actions are mediated through interaction with the G-protein coupled membrane bound melatonin receptors type 1 and type 2 (MT1 and MT2, respectively) or, indirectly with nuclear orphan receptors from the RORα/RZR family. Melatonin also binds to the quinone reductase II enzyme, previously defined the MT3 receptor. Melatonin receptors are widely distributed in the body; herein we summarize their expression and actions in non-neural tissues. Several controversies still exist regarding, for example, whether melatonin binds the RORα/RZR family. Studies of the peripheral distribution of melatonin receptors are important since they are attractive targets for immunomodulation, regulation of endocrine, reproductive and cardiovascular functions, modulation of skin pigmentation, hair growth, cancerogenesis, and aging. Melatonin receptor agonists and antagonists have an exciting future since they could define multiple mechanisms by which melatonin modulates the complexity of such a wide variety of physiological and pathological processes.

The hormone melatonin stimulates renoprotective effects of "early outgrowth" endothelial progenitor cells in acute ischemic kidney injury

Endothelial progenitor cells (EPCs) protect the kidney from acute ischemic injury. The aim of this study was to analyze whether pretreatment of murine "early outgrowth" EPCs (eEPCs) with the hormone melatonin increases the cells' renoprotective effects in the setting of murine acute ischemic renal failure. Male (8-12 wk old) C57Bl/6N mice were subjected to unilateral ischemia-reperfusion injury postuninephrectomy (40 min). Postischemic animals were injected with either 0.5×10(6) untreated syngeneic murine eEPCs or with cells, pretreated with melatonin for 1 h. Injections were performed shortly after reperfusion of the kidney. While animals injected with untreated cells developed acute renal failure, eEPC pretreatment with melatonin dramatically improved renoprotective actions of the cells. These effects were completely reversed after cell pretreatment with melatonin and the MT-1/-2 antagonist luzindole. In vitro analysis revealed that melatonin reduced the amount of tumor growth factor-β-induced eEPC apoptosis/necrosis. Secretion of vascular endothelial growth factor by the cells was markedly stimulated by the hormone. In addition, migratory activity of eEPCs was enhanced by melatonin and supernatant from melatonin-treated eEPCs stimulated migration of cultured mature endothelial cells. In summary, melatonin was identified as a new agonist of eEPCs in acute ischemic kidney injury.

Oxidative stress and inflammation: Implications in uremia and hemodialysis

Oxidative response and inflammation constitute a major defense against infections, but if not properly regulated they could also lead to a number of deleterious effects. Patients affected by different stages of acute and chronic kidney disease, particularly patients on hemodialysis, present a marked activation of oxidative and inflammatory processes. This condition exposes these patients to an elevated risk of morbidity and mortality. This Review is up to date and it analyses the newest notions about pathophysiological mechanisms of oxidative stress and inflammation in patients with renal diseases, also considering the different strategies studied to counterbalance this high risk state.

Deletion of multispecific organic anion transporter Oat1/Slc22a6 protects against mercury-induced kidney injury

The primary site of mercury-induced injury is the kidney due to uptake of the reactive Hg(2+)-conjugated organic anions in the proximal tubule. Here, we investigated the in vivo role of Oat1 (organic anion transporter 1; originally NKT (Lopez-Nieto, C. E., You, G., Bush, K. T., Barros, E. J., Beier, D. R., and Nigam, S. K. (1997) J. Biol. Chem. 272, 6471-6478)) in handling of known nephrotoxic doses of HgCl(2). Oat1 (Slc22a6) is a multispecific organic anion drug transporter that is expressed on the basolateral aspects of renal proximal tubule cells and that mediates the initial steps of elimination of a broad range of endogenous metabolites and commonly prescribed pharmaceuticals. Mercury-induced nephrotoxicity was observed in a wild-type model. We then used the Oat1 knock-out to determine in vivo whether the renal injury effects of mercury are mediated by Oat1. Most of the renal injury (both histologically and biochemically as measured by blood urea nitrogen and creatinine) was abolished following HgCl(2) treatment of Oat1 knock-outs. Thus, acute kidney injury by HgCl(2) was found to be mediated mainly by Oat1. Our findings raise the possibility that pharmacological modulation of the expression and/or function of Oat1 might be an effective therapeutic strategy for reducing renal injury by mercury. This is one of the most striking phenotypes so far identified in the Oat1 knock-out. (Eraly, S. A., Vallon, V., Vaughn, D. A., Gangoiti, J. A., Richter, K., Nagle, M., Monte, J. C., Rieg, T., Truong, D. M., Long, J. M., Barshop, B. A., Kaler, G., and Nigam, S. K. (2006) J. Biol. Chem. 281, 5072-5083).

Melatonin suppresses cyclosporine A-induced autophagy in rat pituitary GH3 cells

Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the induction of chronic nephrotoxicity including endoplasmic reticulum (ER) stress in tubular cells. Recently, it was reported that autophagy is induced by ER stress and serves to alleviate the associated deleterious effects. In the current study, CsA treatment (0-100 microm) decreased cell survival of rat pituitary GH3 cells in a dose-dependent manner. At concentrations ranging from 1.0 to 10 microm, CsA induced a dose-dependent increase in the expression of microtubule-associated protein 1 light chain 3 (LC3)-I and LC3-II. Cells treated with 2.5 microm CsA exhibited cytoplasmic vacuolation, indicating that CsA induces autophagy in rat pituitary GH3 cells. In the presence of 1.0-10 microm CsA, the expression of catalase decreased while that of the ER stress markers, ER luminal binding protein (BiP) and inositol-requiring enzyme 1 alpha (IRE1alpha), increased as compared those levels in untreated cells. These results suggested that CsA-induced autophagy is dependent on ER stress. To determine whether melatonin would protect cells against CsA-induced autophagy, we treated rat pituitary GH3 cells with melatonin in the presence of CsA. Melatonin treatment (100 and 200 microm) suppressed autophagy induced by 2.5 and 5 microm CsA. Furthermore, co-treatment with 100 microm melatonin inhibited LC3-II expression, and increased catalase and phosphorylated p-ERK levels in the presence of 2.5 and 5 microm CsA. BiP and IRE1alpha expression in melatonin-co-treated cells was superior to that in cells treated with 2.5 and 5 microm CsA alone. Thus, melatonin suppresses CsA-mediated autophagy in rat pituitary GH3 cells.

A protein from Cajanus indicus Spreng protects liver and kidney against mercuric chloride-induced oxidative stress

Mercuric chloride (HgCl(2)) is a widespread environmental toxin that affects mainly liver and kidney. The present study has been carried out to investigate the protective action of a protein (the CI protein) isolated from the herb, Cajanus indicus Spreng against HgCl(2) induced renal and hepatic toxicities in mice. Intraperitoneal administration of HgCl(2) at a dose of 5 mg/kg body weight for 1 d significantly reduced the activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Moreover, it also depleted the glutathione to oxidized glutathione (GSH/GSSG) ratio. In addition, HgCl(2) increased the activities of serum marker enzymes (namely, glutamate pyruvate transaminase, GPT and alkaline phosphatase, ALP), creatinine, blood urea nitrogen and serum tumor necrosis factor alpha (TNF-alpha) level along with hepatic and renal lipid peroxidation. Besides, application of HgCl(2) to hepatocytes increased reactive oxygen species production and reduced the total antioxidant activity of the treated hepatocytes. Treatment with the CI protein intraperitoneally at a dose of 2 mg/kg body weight before or after HgCl(2) administration showed that it could scavenge free radicals in vitro and protect the alterations of the antioxidant molecules and the other parameters used in this particular study. Histological studies also revealed a milder lesion in kidney and liver samples of the CI protein treated mice compared to mice treated with HgCl(2) alone. Effects of a known antioxidant N-acetylcysteine have been used to compare its action to that of the CI protein.

IL-6/IL-6R axis plays a critical role in acute kidney injury

The response to tissue injury involves the coordination of inflammatory and repair processes. IL-6 expression correlates with the onset and severity of acute kidney injury (AKI), but its contribution to pathogenesis remains unclear. This study established a critical role for IL-6 in both the inflammatory response and the resolution of AKI. IL-6-deficient mice were resistant to HgCl2-induced AKI compared with wild-type mice. The accumulation of peritubular neutrophils was lower in IL-6-deficient mice than in wild-type mice, and neutrophil depletion before HgCl2 administration in wild-type mice significantly reduced AKI; these results demonstrate the critical role of IL-6 signaling in the injurious inflammatory process in AKI. Renal IL-6 expression and STAT3 activation in renal tubular epithelial cells significantly increased during the development of injury, suggesting active IL-6 signaling. Although a lack of renal IL-6 receptors (IL-6R) precludes the activation of classical signaling pathways, IL-6 can stimulate target cells together with a soluble form of the IL-6R (sIL-6R) in a process termed trans-signaling. During injury,serum sIL-6R levels increased three-fold, suggesting a possible role for IL-6 trans-signaling in AKI. Stimulation of IL-6 trans-signaling with an IL-6/sIL-6R fusion protein activated STAT3 in renal tubular epithelium and prevented AKI. IL-6/sIL-6R reduced lipid peroxidation after injury, suggesting that its protective effect may be largely mediated through amelioration of oxidative stress. In summary, IL-6 simultaneously promotes an injurious inflammatory response and, through a mechanism of trans-signaling, protects the kidney from further injury.

Melatonin ameliorates oxidative stress, inflammation, proteinuria, and progression of renal damage in rats with renal mass reduction

The progressive deterioration of renal function and structure resulting from renal mass reduction are mediated by a variety of mechanisms, including oxidative stress and inflammation. Melatonin, the major product of the pineal gland, has potent_antioxidant and anti-inflammatory properties, and its production is impaired in chronic renal failure. We therefore investigated if melatonin treatment would modify the course of chronic renal failure in the remnant kidney model. We studied rats followed 12 wk after renal ablation untreated (Nx group, n = 7) and treated with melatonin administered in the drinking water (10 mg/100 ml) (Nx + MEL group, n = 8). Sham-operated rats (n = 10) were used as controls. Melatonin administration increased 13-15 times the endogenous hormone levels. Rats in the Nx + MEL group had reduced oxidative stress (malondialdehyde levels in plasma and in the remnant kidney as well as nitrotyrosine renal abundance) and renal inflammation (p65 nuclear factor-kappaB-positive renal interstitial cells and infiltration of lymphocytes and macrophages). Collagen, alpha-smooth muscle actin, and transforming growth factor-beta renal abundance were all increased in the remnant kidney of the untreated rats and were reduced significantly by melatonin treatment. Deterioration of renal function (plasma creatinine and proteinuria) and structure (glomerulosclerosis and tubulointerstitial damage) resulting from renal ablation were ameliorated significantly with melatonin treatment. In conclusion, melatonin administration improves the course of chronic renal failure in rats with renal mass reduction. Further studies are necessary to define the potential usefulness of this treatment in other animal models and in patients with chronic renal disease.

Mycophenolate mofetil treatment improves hypertension in patients with psoriasis and rheumatoid arthritis

Evidence that was obtained in several experimental models and in strains of hypertensive rats indicates that infiltration of inflammatory cells and oxidative stress in the kidney play a role in the induction and maintenance of hypertension. Similar evidence is lacking in human hypertension, at least in part, because immunosuppressive treatment is unjustified in patients with hypertension. For addressing this issue, patients who were prescribed by their private physicians mycophenolate mofetil (MMF) for the treatment of psoriasis or rheumatoid arthritis and had, in addition, grade I essential hypertension and normal renal function were studied. Eight patients were studied before MMF was started, during MMF treatment, and 1 mo after MMF treatment had been discontinued. Other treatments and diet were unchanged in the three phases of the study. MMF therapy was associated with a significant reduction in systolic, diastolic, and mean BP. Urinary excretion of TNF-alpha was reduced progressively by MMF treatment and increased after MMF was discontinued. Reduction of urinary malondialdehyde, TNF-alpha, and RANTES excretion during MMF administration did not reach statistical significance but had a direct positive correlation with the BP levels. These data are consistent with the hypothesis that renal immune cell infiltration and oxidative stress play a role in human hypertension.

Aging impairs neurogenic contraction in guinea pig urinary bladder: role of oxidative stress and melatonin

The incidence of urinary bladder disturbances increases with age, and free radical accumulation has been proposed as a causal factor. Here we investigated the association between changes in bladder neuromuscular function and oxidative stress in aging and the possible benefits of melatonin treatment. Neuromuscular function was assessed by electrical field stimulation (EFS) of isolated guinea pig detrusor strips from adult and aged female guinea pigs. A group of adult and aged animals were treated with 2.5 mg·kg−1·day−1 melatonin for 28 days. Neurotransmitter blockers were used to dissect pharmacologically the EFS-elicited contractile response. EFS induced a neurogenic and frequency-dependent contraction that was impaired by aging. This impairment is in part related to a decrease in detrusor myogenic contractility. Age also decreased the sensitivity of the contraction to pharmacological blockade of purinergic and sensitive fibers but increased the effect of blockade of nitrergic and adrenergic nerves. The density of cholinergic and nitrergic nerves remained unaltered, but aging modified afferent fibers. These changes were associated with an increased level of markers for oxidative stress. Melatonin treatment normalized oxidative levels and counteracted the aging-associated changes in bladder neuromuscular function. In conclusion, these results show that aging modifies neurogenic contraction and the functional profile of the urinary bladder plexus and simultaneously increases the oxidative damage to the organ. Melatonin reduces oxidative stress and improves the age-induced changes in bladder neuromuscular function, which could be of importance in reducing the impact of age-related bladder disorders.

Melatonin reduces uranium-induced nephrotoxicity in rats

The protective role of exogenous melatonin on U-induced nephrotoxicity was investigated in rats. Animals were given single doses of uranyl acetate dihydrate (UAD) at 5 mg/kg (subcutaneous), melatonin at 10 or 20 mg/kg (intraperitoneal), and UAD (5 mg/kg) plus melatonin (10 or 20 mg/kg), or vehicle (control group). In comparison with the UAD-treated group only, significant beneficial changes were noted in some urinary and serum parameters of rats concurrently exposed to UAD and melatonin. The increase of U excretion after UAD administration was accompanied by a significant reduction in the renal content of U when melatonin was given at a dose of 20 mg/kg. Melatonin also reduced the severity of the U-induced histological alterations in kidney. In renal tissue, the activity of the superoxide dismutase (SOD) and the thiobarbituric acid reactive substances (TBARS) levels increased significantly as a result of UAD exposure. Following UAD administration, oxidative stress markers in erythrocytes showed a reduction in SOD activity and an increase in TBARS levels, which were significantly restored by melatonin administration. In plasma, reduced glutathione (GSH) and its oxidized form (GSSG) were also altered in UAD-exposed rats. However, only the GSSG/GSH ratio was restored to control levels after melatonin treatment. Oxidative damage was observed in kidneys. Melatonin administration partially restored these adverse effects. It is concluded that melatonin offers some benefit as a potential agent to treat acute U-induced nephrotoxicity.

Mycophenolate mofetil administration reduces renal inflammation, oxidative stress, and arterial pressure in rats with lead-induced hypertension

Hypertension is a likely consequence of chronic lead exposure in humans, especially in association with reduced renal function and in high risk populations. Numerous studies have demonstrated that oxidative stress plays an important role in the pathogenesis of experimental lead-induced hypertension and we have shown recently that tubulointerstitial immune cell infiltration is a feature of chronic low-dose lead exposure. Since oxidative stress, renal inflammation, and angiotensin activity are closely linked characteristics in experimental models of hypertension, we decided to investigate whether lead-induced hypertension would be ameliorated by suppressing renal inflammation with the immunosuppressive drug mycophenolate mofetil (MMF). We studied rats exposed for 14 wk to lead acetate (100 ppm in the drinking water) that, in addition, received either MMF, 20 mg.kg(-1).day(-1) by gastric gavage (Pb.MMF group, n = 12) or vehicle (Pb group, n = 12). Control rats received MMF alone (n = 5) or neither lead nor MMF (n = 6). All rats were killed at the end of the experiment. Low-dose lead exposure resulted in mild to moderate tubular cell damage and a progressive increment in blood pressure, oxidative stress, interstitial accumulation of lymphocytes and macrophages, NF-kappaB activation, and increased renal angiotensin II level. The administration of MMF suppressed the tubulointerstitial accumulation of lymphocytes and macrophages and prevented the hypertension, oxidative stress, and NF-kappaB activation and reduced the heightened renal angiotensin content associated with chronic lead exposure. We conclude that interstitial inflammation plays an important role in lead-induced hypertension.

Eruca sativa seeds possess antioxidant activity and exert a protective effect on mercuric chloride induced renal toxicity

Mercuric chloride (HgCl(2)) is a well-known nephrotoxic agent. Increasing number of evidences suggest the role of oxidative stress in HgCl(2) induced nephrotoxicity. Eruca sativa is widely used in folklore medicines and has a good reputation as a remedy of renal ailments. In the present study, the antioxidant potential of ethanolic extract of E. sativa seeds was determined and its protective effect on HgCl(2) induced renal toxicity was investigated. The extract was found to possess a potent antioxidant effect, with a large amount of polyphenols and a high reducing ability. HPLC analysis of the extract revealed glucoerucin and flavonoids to be the major antioxidants present in it. E. sativa extract significantly scavenged several reactive oxygen species (ROS) and reactive nitrogen species (RNS). Feeding of the extract to rats afforded a significant protection against HgCl(2) induced renal toxicity. Subcutaneous administration of 4 mg/kg body weight HgCl(2) induced renal injury evident as a marked elevation in serum creatinine and blood urea nitrogen levels, and histopathological changes such as necrosis, oedema and congestion of stroma and glomeruli. Oxidative modulation of renal tissues following HgCl(2) exposure was evident from a significant elevation in lipid peroxidation and attenuation in glutathione (GSH) contents and activities of antioxidant enzymes viz., catalase (CAT), glutathione peroxidase (GPX), superoxide dismutase (SOD) and glutathione reductase (GR). Oral administration of E. sativa extract to rats at a dose regimen: 50-200 mg/kg body weight for 7 days prior to HgCl(2) treatment significantly and dose dependently protected against alterations in all these diagnostic parameters. The data obtained in the present study suggests E. sativa seeds to possess a potent antioxidant and renal protective activity and preclude oxidative damage inflicted to the kidney.

A novel method for the evaluation of proximal tubule epithelial cellular necrosis in the intact rat kidney using ethidium homodimer

BACKGROUND

Ethidium homodimer is a cell-membrane impermeant nuclear fluorochrome that has been widely used to identify necrotic cells in culture. Here, we describe a novel technique for evaluating necrosis of epithelial cells in the proximal tubule that involves perfusing ethidium homodimer through the intact rat kidney. As a positive control for inducing necrosis, rats were treated with 3.5, 1.75, 0.87 and 0.43 mg/kg mercuric chloride (Hg2+, intraperitoneal), treatments which have previously been shown to rapidly cause dose-dependent necrosis of the proximal tubule. Twenty-four h after the administration of Hg2+, ethidium homodimer (5 microM) was perfused through the intact left kidney while the animal was anesthetized. The kidney was then removed, placed in embedding medium, frozen and cryosectioned at a thickness of 5 microm. Sections were permeabilized with -20 degrees C methanol and then stained with 4',6-diamidino-2-phenylindole (DAPI) to label total nuclei. Total cell number was determined from the DAPI staining in random microscopic fields and the number of necrotic cells in the same field was determined by ethidium homodimer labeling.

RESULTS

The Hg2+-treated animals showed a dose-dependent increase in the number of ethidium labeled cells in the proximal tubule, but not in other segments of the nephron. Other results showed that a nephrotoxic dose of gentamicin also caused a significant increase in the number of ethidium labeled cells in the proximal tubule.

CONCLUSION

These results indicate that this simple and sensitive perfusion technique can be used to evaluate cellular necrosis in the proximal tubule with the three-dimensional cyto-architecture intact.

Contrast-induced nephropathy: preventive and protective effects of melatonin

Infusion of contrast agents increases osmotic load, viscosity, hypoxemia of the renal medulla and renal free radical production through post-ischemic oxidative stress. The present experimental study sought to determine whether melatonin, because of its anti-oxidant properties might have a preventive and protective role against the development of contrast-induced nephropathy (CIN). Twenty-four adult male rats were divided into four experimental groups: healthy control rats (CR), rats with CIN (CINR), rats with CIN pretreated with melatonin (CINR1M), and rats with CIN pre- and post-treated with melatonin (CINR2M). In CINR, both serum creatinine (Cr) level and fractional excretion of sodium (FE-Na) significantly increased, whereas Cr clearance decreased at post-CIN compared with pre-CIN period. Rats in CINR1M did not show any improvement in renal function. Cr clearance decreased, whereas both serum Cr level and FE-Na increased in rats pretreated with melatonin. In contrast, significant improvements were observed in CINR2M. Serum Cr and Cr clearance did not change, whereas FE-Na significantly reduced in rats pre- and post-treated with melatonin. In conclusion, the present experimental study clearly demonstrated the preventive and protective role of melatonin against the development of CIN.

Tubular stress proteins and nitric oxide synthase expression in rat kidney exposed to mercuric chloride and melatonin

Stress proteins such as HSP70 members (HSP72 and GRP75) and metallothionein (MT) protect the kidney against oxidative damage and harmful metals, whereas inducible nitric oxide synthase (iNOS) regulates tubular functions. A single dose of mercuric chloride (HgCl(2)) can cause acute renal failure in rats, its main target being the proximal tubule. Oxidative damage has been proposed as one of its pathogenic mechanisms. In this study we tested whether melatonin (MEL), a powerful antioxidant compound, is effective against HgCl(2) nephrotoxicity. Rats were treated with saline, HgCl(2) (3.5 mg/kg), MEL (5 mg/kg), and MEL + HgCl(2) and examined after 24 hr for HSP72, GRP75, MT, and iNOS by immunohistochemistry and immunoblotting. Tubular effects of the treatment were then characterized by ultrastructure. In the HgCl(2) group, all markers were overexpressed in convoluted proximal tubules and sometimes in distal tubules. In the MEL + HgCl(2) group, GRP75 and iNOS decreased in convoluted and straight proximal tubules, whereas HSP72 and MT persisted more than the saline and MEL-only groups. Tubular damage and mitochondrial morphometry were improved by MEL pretreatment. In conclusion, the beneficial effect of MEL against HgCl(2) nephrotoxicity was outlined morphologically and by the reduction of the tubular expression of stress proteins and iNOS. These markers could represent sensitive recovery index against mercury damage.

Urinary marker for oxidative stress in kidneys in cisplatin-induced acute renal failure in rats

BACKGROUND

Establishment of non-invasive urinary biomarkers for the prediction of acute renal failure (ARF) is important. We evaluated whether urinary oxidative stress markers reflect intrarenal oxidative stress in cisplatin (CDDP)-induced ARF, and whether these markers can be used for the prediction of future ARF.

METHODS

Urinary malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured up to day 14 post-CDDP (6 mg/kg) injection in rats. MDA and 8-OHdG expressions were examined in kidneys.

RESULTS

CDDP induced an increase in serum creatinine (Scr), blood urea nitrogen (BUN), and tubular damage at day 5, increased urinary MDA excretion and MDA expression in kidneys at day 1 (but returned to basal values by day 3), increased urinary excretion of 8-OHdG at day 5 till day 14 (though the number of 8-OHdG-positive tubular cells increased at day 5 and then gradually decreased). Urinary MDA levels at day 1 correlated significantly with Scr (rho = 0.721, P < 0.01) and tubular damage score (rho = 0.840, P < 0.01) at day 5.

CONCLUSION

Our findings demonstrated divergent changes of urinary oxidative stress markers in CDDP-induced ARF, and suggested that urinary MDA may be a useful marker for the prediction of the development of CDDP-induced ARF.

Hypertension in Page (cellophane-wrapped) kidney is due to interstitial nephritis

BACKGROUND

Cellophane wrapping of the kidneys (Page kidney) induces perinephrits and hypertension, assumed to be due to renal ischemia resulting from parenchymal compression by the fibrous hull surrounding the kidneys. We investigated if interstitial nephritis, rather than plasma angiotensin activity, played a role in the development of hypertension in the Page kidney model.

METHODS

We followed for 7 weeks rats with bilateral cellophane wrapping of the kidneys that received 20 mg/kg/day of the immunosuppressive antiproliferative drug mycophenolate mofetil (MMF) (two-kidney wrap/MMF) (N = 10) or vehicle (two-kidney wrap) (N = 10), and sham-operated rats (N = 10).

RESULTS

The two-kidney wrap group had progressive increment in blood pressure, inflammatory damage occupying 25% to 50% of the renal tubulointerstitial region and increased number of angiotensin II-positive cells, angiotensin II content, and oxidative stress in the kidney. MMF treatment prevented the development of hypertension and renal inflammation without modifying the perinephritic hull or the increment it induced in the intrarenal pressure. The plasma levels of angiotensin II were similar in the two-kidney wrap group, the two-kidney wrap/MMF group and the sham-operated animals and unchanged from baseline, despite the blood pressure increase in the two-kidney wrap group.

CONCLUSION

Our results indicate that renal wrap hypertension is unrelated to plasma angiotensin II levels and related to the inflammatory damage caused by the external compression of the kidney.

Melatonin mitigates mitochondrial malfunction

Melatonin, or N-acetyl-5-methoxytryptamine, is a compound derived from tryptophan that is found in all organisms from unicells to vertebrates. This indoleamine may act as a protective agent in disease conditions such as Parkinson's, Alzheimer's, aging, sepsis and other disorders including ischemia/reperfusion. In addition, melatonin has been proposed as a drug for the treatment of cancer. These disorders have in common a dysfunction of the apoptotic program. Thus, while defects which reduce apoptotic processes can exaggerate cancer, neurodegenerative disorders and ischemic conditions are made worse by enhanced apoptosis. The mechanism by which melatonin controls cell death is not entirely known. Recently, mitochondria, which are implicated in the intrinsic pathway of apoptosis, have been identified as a target for melatonin actions. It is known that melatonin scavenges oxygen and nitrogen-based reactants generated in mitochondria. This limits the loss of the intramitochondrial glutathione and lowers mitochondrial protein damage, improving electron transport chain (ETC) activity and reducing mtDNA damage. Melatonin also increases the activity of the complex I and complex IV of the ETC, thereby improving mitochondrial respiration and increasing ATP synthesis under normal and stressful conditions. These effects reflect the ability of melatonin to reduce the harmful reduction in the mitochondrial membrane potential that may trigger mitochondrial transition pore (MTP) opening and the apoptotic cascade. In addition, a reported direct action of melatonin in the control of currents through the MTP opens a new perspective in the understanding of the regulation of apoptotic cell death by the indoleamine.

Protective effects of melatonin against carbon tetrachloride hepatotoxicity in rats

Melatonin is an indolamine, mainly secreted by the pineal gland into the blood of mammalian species. The potential for protective effects of melatonin on carbon tetrachloride (CCl(4))-induced acute liver injury in rats was investigated in this work. CCl(4) exerts its toxic effects by generation of free radicals; it was intragastrically administered to male Wistar rats (4 g kg(-1) body weight) at 20 h before the animals were decapitated. Melatonin (15 mg kg(-1) body weight) was administered intraperitoneally three times: 30 min before and at 2 and 4 h after CCl(4) injection. Rats injected with CCl(4) alone showed significant lipid and hydropic dystrophy of the liver, massive necrosis of hepatocytes, marked increases in free and conjugated bilirubin levels, elevation of hepatic enzymes (alanine aminotransferase and aspartate aminotransferase) in plasma, as well as NO accumulation in liver and in blood. Melatonin administered at a pharmacological dose diminished the toxic effects of CCl(4). Thus it decreased both the structural and functional injury of hepatocytes and clearly exerted hepatoprotective effects. Melatonin administration also reduced CCl(4)-induced NO generation. These findings suggest that the effect of melatonin on CCl(4)-induced acute liver injury depends on the antioxidant action of melatonin.

Melatonin Protects Against Mercury(II)-Induced Oxidative Tissue Damage in Rats

Mercury exerts a variety of toxic effects in the body. Lipid peroxidation, DNA damage and depletion of reduced glutathione by Hg(II) suggest an oxidative stress-like mechanism for Hg(II) toxicity. Melatonin, the main secretory product of the pineal gland, was recently found to be a potent free radical scavenger and antioxidant. N-Acetylcysteine, a precursor of reduced glutathione and an antioxidant, is used in the therapy of acute heavy metal poisoning. In this study the protective effects of melatonin in comparison to that of N-acetylcysteine against Hg-induced oxidative damage in the kidney, liver, lung and brain tissues were investigated. Wistar albino rats of either sex (200-250 g) were divided into six groups, each consisting of 8 animals. Rats were intraperitoneally injected with 1) 0.9% NaCl, control (C) group; 2) a single dose of 5 mg/kg mercuric chloride (HgCl2), Hg group; 3) melatonin in a dose of 10 mg/kg, 1 hr after HgCl2 injection, Hg-melatonin group; 4) melatonin in a dose of 10 mg/kg one day before and 1 hr after HgCl2 injection, melatonin-Hg-melatonin group; 5) N-acetylcysteine in a dose of 150 mg/kg, 1 hr after HgCl2 injection, Hg-N-acetylcysteine group, and 6) N-acetylcysteine in a dose of 150 mg/kg one day before and 1 hr after HgCl2 injection, N-acetylcysteine-Hg-N-acetylcysteine group. Animals were killed by decapitation 24 hr after the injection of HgCl2. Tissue samples were taken for determination of malondialdehyde, an end-product of lipid peroxidation; glutathione (GSH), a key antioxidant, and myeloperoxidase activity, an index of neutrophil infiltration. The results revealed that HgCl2 induced oxidative tissue damage, as evidenced by increases in malondialdehyde levels. Myeloperoxidase activity was also increased, and GSH levels were decreased in the liver, kidney and the lungs. All of these effects were reversed by melatonin or N-acetylcysteine treatment. Since melatonin or N-acetylcysteine administration reversed these responses, it seems likely that melatonin or N-acetylcysteine can protect all these tissues against HgCl2-induced oxidative damage.

Apoptosis and NFkappaB activation are simultaneously induced in renal tubulointerstitium in experimental hypertension

BACKGROUND

Oxidative stress is known to induce apoptosis and activation of pro-inflammatory transcription factor nuclear factor kappa B (NFkappaB), which are biologic effects that may play a role in the renal damage associated with arterial hypertension. We investigated if increased apoptosis and NFkappaB activation were present in experimental models of hypertension.

METHODS

Sprague-Dawley rats fed with regular rodent chow and free access to water were studied. The Ang II group (N = 6) received 435 ng/kg/min of angiotensin II during 2 weeks by subcutaneous minipumps. The l-NAME group (N = 5) received Nomega-nitro-l-arginine-methyl-ester (l-NAME) in the drinking water (70 mg/100 mL) for 3 weeks. The control group consisted of 6 rats. Systolic blood pressure (tail cuff plethysmography), serum creatinine, and proteinuria were determined weekly. Kidneys were examined for superoxide-positive cells (histochemistry) and for apoptosis [terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick-end labeling (TUNEL)-positive cells], proliferation [proliferating cell nuclear antigen (PCNA)-positive cells), and activation of NFkappaB (p65 subunit) with the appropriate antibodies.

RESULTS

As expected, hypertension developed in experimental groups. Tubulointerstitial superoxide-positive cells were increased 7 times (P < 0.001), TUNEL-positive cells were increased 3 to 4 times (P < 0.001), PCNA-positive cells were increased 20 to 30 times (P < 0.001), and NFkappaB activation was increased 4 to 5 times (P < 0.001) in the experimental groups. NFkappaB expression correlated with the number of interstitial lymphocytes (r = 0.667, P < 0.01) and macrophages (r = 0.835, P < 0.001).

CONCLUSION

Angiotensin II infusion and l-NAME administration induce oxidative stress and increased apoptosis and activation of the transcription factor NFkappaB. These effects may participate in the development of progressive renal injury resulting from uncontrolled hypertension

Prevention of apoptotic and necrotic cell death, caspase-3 activation, and renal dysfunction by melatonin after ischemia/reperfusion

The pineal hormone melatonin has been reported to protect tissue from oxidative damage. This study was designed to determine whether melatonin could prevent cell events leading to tissue injury and renal dysfunction after ischemia/reperfusion (I/R). Using an in vivo rat model of I/R, we show a significant increase in kidney malondialdehyde concentrations, reflecting lipid peroxidation, and cell apoptosis measured by TUNEL staining. This apoptotic cell death was associated with an increase in the activity of the proapoptotic factor caspase-3, determined by fluorometric protease activity assay. Histomorphological analysis of ischemic kidneys revealed that the most extensive tubular necrosis occurred at 24 and 48 h after reperfusion, which correlated with peak elevations in blood urea nitrogen and creatinine. Rat pretreatment with melatonin prevented lipid peroxidation, cell apoptosis, and necrosis and blocked caspase-3 activity. The prevention of tissue injury was associated with the improvement of renal function as shown by the decrease in blood urea nitrogen and creatinine concentrations. The demonstration that melatonin prevents postreperfusion apoptotic and necrotic cell death and improves renal function suggests that melatonin may represent a novel therapeutic approach for prevention of I/R injury.